Difference between network load for FastBack DEDUP versus without DEDUP

Technote (troubleshooting)

Problem(Abstract)

The FastBack DEDUP system uses the TCP/IP stack to connect to the FastBack Server. This is a major difference between a DEDUP and non-DEDUP FastBack system. When a TCP/IP stack overload exists, this can result in network performance issues for a system using Deduplication.

Symptom

A Fastback system without Deduplication may function correctly and then suddenly encounter problems after Deduplication is enabled.

For example a FastBack snapshot may be aborted with different communication errors shown in the FastBack Manager -> Snapshots Monitor -> Aborted snapshots Events

Cause

For a machine that is heavily used and has limited resources or network bandwidth, failures may be witnessed due to the intensive usage of the local TCP stack when enabling an additional network using service such as FastBack DEDUP.

Resolving the problem

The following considerations can be used to help alleviate these types of network problems:

1. The load on the internal TCP stack should be decreased. That can be done by investigating the OS, environment and applications services, which use the TCP stack for internal and external connections and by disabling (permanently or temporarily) non-vital network using services.

Note: disabling the non-vital network services needs to be determined for each individual business environment and it is the responsibility of the business to make this decision. For more information about changing the state of a specific application we strongly recommend to first consult with the service provider or vendor.

2. Enabling/Disabling the TCP Offload Engine may improve (or worsen) the situation. In some cases by turning off the TCP Offload option (which is enabled by default from Windows VISTA or greater systems) may solve the network issues in the systems with intensive TCP stack usage.

Note: The decision to change the state of the TCP Offload function is again the responsibility of the individual business. We strongly recommend to consult with Microsoft Support regarding the TCP Offload state before applying any change since other OS, environment, services or applications in the same system may be dependent upon that function state.